The present invention relates to the preparation of aqueous solutions of polysaccharide.
The preparation of an aqueous solution of polysaccharide into a viscous solution is generally well known in the art. It is desirable when preparing an aqueous solution of polysaccharide to be able to control the ultimate viscosity of the solution and particularly desirable to be able to increase the viscosity of the solution without using additional polysaccharide. A typical use of polysaccharide solutions is in a water flood operation to recover oil from subterranean reservoirs. These processes are well known in the petroleum production art. Aqueous polysaccharide solutions are injected to follow an aqueous flooding medium, for example; water, surfactant or other recovery agents to drive oil in the reservoir to one or more production wells where oil is produced. The tendency of injected water to channel through the sweeping medium and completely bypass portions of the reservoir is a well known problem. The problem has been overcome by the use of viscous solutions of polymers such as polysaccharide.
Researchers and practioners of the art have taught that a polysaccharide solution may be prepared in water containing a high content of inorganic ions. Since most of the water in an oil field contains a considerable amount of inorganic ions it is convenient to add the polysaccharide directly to the brine water to be used in the recovery operation. This, of course, leads to a viscous aqueous solution but the viscosity is not always as high as is desired using the amount of polysaccharide necessary for an economical recovery operation. It has been surprisingly discovered that the viscosity of the aqueous brine solution of polysaccharide can be increased dramatically without additional polysaccharide by the method to be disclosed herein.